Super-Angulon-R 21mm f4, 3-cam. Serial number in the 3,080,000 range, manufactured in 1980. Leitz catalog number 11813.
Introduced in 1968 for the Leicaflex SL. While the maximum aperture was reduced compared to its f3.4 predecessor, the rear element protrusion was made smaller, eliminating the need for mirror lock-up. Initially produced as a 2-cam lens, it was changed to 3-cam from 1977 onward. It remained in production until 1992, making it a long-selling lens.
This was Leica’s first retrofocus lens, manufactured by Schneider on an OEM basis. The optical construction consists of 8 groups and 10 elements. With multiple elements used for correction, it offers minimal distortion, high resolution, and reduced vignetting, making it an outstanding performer.

The minimum focusing distance is 0.2 m. Distance scale is in both feet and meters. Filters are either Series 8.5, inserted into the hood, or 72 mm screw-in filters.